Pulverizer with fixed-arm spacer assembly

ABSTRACT

Apparatus is provided for pulverizing raw coal feed stock into comminuted particles which can be conveyed to the combustion chamber of a furnace. A fixed arm spacer assembly is mounted on the pulverizer table such that the pulverizer rollers are separated from each other to prevent skidding.

O Umted States Patent 1191 [111 3,776,478 Gillette et al. Dec. 4, 1973[54] PULVERIZER WITH FIXED-ARM SPACER 3,458,142 7/1969 Berz 241/103ASSEMBLY 3,606,179 9/1971 Romanowski et a1 241/103 3,612,418 10/1971Barton 241/103 X 1 Inventors Robert Gillette, Randolph 1,401,716 12 1921McCrae 241 104 Township; Henry P. Kunz, Glen Ridge both of Ni FOREIGNPATENTS OR APPLICATIONS 943,176 12/1963 Great Britain 241/117 AsslgneerFoster Wheeler Corporation, 1,361,757 4/1964 France 241/117 Livingston,NJ. 22 Filed: May 4, 1971 Primary Examiner-Robert L. SpruillAttorney-John Maier, 111, Marvin A. Naigur and John [211 App]. No.:140,173 5 Wilson 52 US. Cl. 241/103 1 1 ABSTRACT [51] Int. Cl. B02c15/00 Apparatus is provided for pulverizing raw coal feed [58] Field ofSearch 241/103, 110, 117, stock into comminuted particles which can becon- 241/118, 119, 120, 104, 173 veyed to the combustion chamber of afurnace. A

fixed arm spacer assembly is mounted on the pulver- [56] ReferencesCited izer table such that the pulverizer rollers are separated UNITEDSTATES PATENTS from each other to prevent skidding.

3,454,231 7/ 1969 Engler 241/103 3 Claims, 3 Drawing Figures PATENTEDBEBMSIS' 3'776'478 SHEET 10F 2 INVENTORS ROBERT P GILLETTE BY HENRY KUNZATTORNEY PULVERIZER WITI-I FIXED-ARM SPACER ASSEMBLY BACKGROUND OF THEINVENTION In connection with the operation of relatively large coalfired furnaces which are used in vapor generating systems in the utilityindustry for production of electricity, it is necessary to supply finelypowdered coal to the combustion chamber of the furnace. The raw coalfeed stock is usually reduced to comminuted particles in a pulverizerapparatus which generally consists of a rotating grinding table on whichthere is formed a grinding surface, and relatively heavy rollers arejournaled within the apparatus and maintained in contact with thegrinding surface by a thrust ring.

There has recently developed a major problem in connection with thepulverizing of coal feed stocks containing particles which cannot easilybe pulverized by the apparatus, such as iron pyrite and the like. Theserelatively hard constituents are more commonly found in many types ofcoal which are being mined today. The hard particles often prevent thepulverizing apparatus from functioning efficiently, in that skiddingaction is translated to the rollers. In accordance with the presentinvention, the skidding of the rollers has been alleviated by providinga fixedarm spacer assembly with contact pads mounted at the end of eacharm. In this manner, the rolling action of any two of the pulverizerrollers can restore a jammed or skidding third pulverizer roller back toa rolling mode of operation. By fixing spacer arms and therebymaintaining pulverizer roller separation, it is possible for force to betransmitted from one pulverizer roller through the hub assembly toanother roller. Also, the spacer assembly prevents bunching of therollers which often is caused by either differences in the pulverizerroller size or obstructions to one or more of the pulverizer rollers.This type of condition creates severe breaking action in one of therollers and often results in the three rollers simultaneously effectinga skidding mode of operation.

In the past, pulverizers have been used with spacer assembliesconsisting of a fixed-arm and two pivoted arms, such that the rollerstransmit force to each other through wear pads positioned between therollers, thereby relieving the spacer arms and hub structure of forcetransmittance. In this type of pivoted spacer design when one of therollers began to skid, this would cause the remaining rollers to bunchtogether, and subsequently all of the rollers would enter into askidding mode of operation. In accordance with the present invention,roller separation is maintained by the fixed arms and when one of therollers goes into a skid, force is then transmitted from this skiddingroller through the hub assembly to one of the other rollers. Dependingon the relative speed of the skidding roller, the rotating fixed arms oneither side of it will speed it up or slow it down to bring it out ofthe skid.

SUMMARY OF THE INVENTION In accordance with an illustrative embodimentdemonstrating features and advantages of the present invention, there isprovided an apparatus for pulverizing material into comminuted particlesincluding a housing and a table having a grinding surface mounted in thehousing for rotation. Means are provided for rotating the table and forintroducing the material into the housing in contact with the grindingsurface. A plurality of rollers are mounted for rotation about theirrespective axes and each of the rollers have a peripheral grinding facemaintained in contact with the grinding surface, and a thrust ring ismounted in contact with the rollers. Mounted on the table is a spacermeans which includes a fixed arm between each of the rollers and acontact pad mounted at the end of each fixed arm. In this manner, therollers are separated from each other and are prevented from skidding,whereby the rollers travel along the table without rotating about theirrespective axes and slide along the thrust ring.

BRIEF DESCRIPTION OF THE DRAWINGS The above brief description as well asfurther objects, features, and advantages of the present invention willbe more fully appreciated by referring to the following description of apresently preferred but nonetheless illustrative embodiments inaccordance with the present invention when taken in connection with theaccompanying drawings, wherein:

FIG. 1 is a front sectional view of a portion of a pulverizing apparatusembodying features of the present invention;

FIG. 2 is an enlarged sectional view of part of the fixed arm spacerassembly, showing an enlarged portion of the spacer hub; and

FIG. 3 is an enlarged plan view of the rollers and spacer assembly, aportion of which has been sectioned to better show the hub and contactpads.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, apulverizing apparatus is shown which is generally designated by thereference numeral 10. The pulverizing apparatus 10 includes a steelhousing 12 which is mounted at ground level for enclosing a rotatablymounted grinding unit 14. Raw coal feed stock is introduced into thehousing 12 through a conduit system 16 which is generally positionedabove the grinding unit 14.

The grinding unit 14 includes a table 20 on which there is mounted aremovable grinding ring 22 formed with an annular groove 24. The table20 is mounted for rotation on a support and is powered by an electricmotor which has not been shown in the drawings for the sake ofsimplicity.

A plurality of spaced apart pulverizing rollers 26, preferably three innumber, are mounted for rotation about their respective axes. Each ofthe rollers 26 has a peripheral grinding face which is maintained incontact with the outer grinding surface of annular groove 24. Therollers 26 are also formed with a bearing collar 30 which has an annulargroove 32. A thrust ring 34 is mounted in housing 12 above thepulverizing rollers 26, and load is applied by means of compressionsprings 36. The thrust ring 34 is integrally formed with an annular lip38 which is configurated in accordance with the outer periphery ofannular groove 32 in order to achieve smooth mating contact.

In accordance with the present invention a spacer assembly 40 is mountedabove the grinding ring 22 by means of a shaft 42 which is fixed to thetable 20 for rotation therewith. The spacer assembly 40 includes a hubsection 44 having a hollow cylindrical bearing unit 46 on which there ismounted fixed arms 48. As best shown in FIG. 2, hub section 44 includesa lower annular ring bearing 50 and an upper ring bearing 51 mounted onthe interior of bearing unit 46 for respectively engaging a lower sleevebearing 52 and an upper throat bearing 54 which are mounted on the shaft42. Fron the relatively large bearing clearances shown in FIG. 2, it canbe appreciated that spacer assembly 40 is loosely mounted for rotationon shaft 42, such that axial rotation as well as pivotal movement can beachieved by spacer assembly 40 with respect to the central axis of shaft42.

A contact assembly generally designated 56 is mounted at the ends ofeach of the fixed arms 48. The contact assembly 56 generally consists ofa replaceable contact block 58 having a frustoconical cross-sectionwhich is mounted at the end of the fixed arm 48 by means of a shaft 60formed with a slot 62 for receiving a lower wedge 64 and an upper wedge66. As shown in FIG. 3, the lower wedge 64 is larger than upper wedge66, which is secured by a weld connection 68, that can be broken forremoving the contact blocks 58. To achieve greater structural stability,the spacer means 40 is provided with an upper spider plate 70 and alower spider plate 72 which are welded to the fixed arms 48.

During the operation of the pulverizing apparatus 10, it can beappreciated that the spacer assembly 40 rotates on shaft 42 inaccordance with the force transmitted by the rollers 26 to the contactassembly 56. Thus, it is possible to operate the pulverizing apparatuswith the rollers 26 traveling along the table without rotating abouttheir respective axes and sliding along the thrust ring 34.

A latitude of modification, change and substitution is intended in theforegoing disclosure and in some instances some features of theinvention will be employed without a corresponding use of otherfeatures.

What is claimed is:

1. Apparatus for pulverizing material into comminuted particlescomprising a housing, a table having a grinding surface defined by acircumferential path mounted in said housing for rotation, means forrotating said table, means for introducing said material into saidhousing in contact with said grinding surface, a plurality of rollersmounted for rotation about their respective axes and each of the rollershaving a peripheral grinding face maintained in contact with said table,and spacer means mounted on said table including a fixed arm betweeneach of said rollers and contact means mounted at the end of said fixedarm for separating said rollers from each other along saidcircumferential path such that said rollers are prevented from skidding,said spacer means including a shaft fixed to said table and a hubrotatably mounted on said shaft with each of the fixed arms mounted onand extending outwardly from said hub, and said hub formed with anintemal bearing surface for engagement with external bearing meansmounted on said shaft, and said internal bearing surface and saidexternal bearing means configurated to afford axial and pivotal movementof said spacer means with respect to said shaft.

2. Apparatus according to claim 1 in which said external bearing meansincludes a sleeve bearing located in a position spaced apart from theend of said shaft, and a thrust bearing mounted on the end of saidshaft.

3. Apparatus according to claim 1 in which said contact means includes areplaceable block having a frusmounted on the end of said fixed arm.

1. Apparatus for pulverizing material into comminuted particlescomprising a housing, a table having a grinding surface defined by acircumferential path mounted in said housing for rotation, means forrotating said table, means for introducing said material into saidhousing in contact with said grinding surface, a plurality of rollersmounted for rotation about their respective axes and each of the rollershaving a peripheral grinding face maintained in contact with said table,and spacer means mounted on said table including a fixed arm betweeneach of said rollers and contact means mounted at the end of said fixedarm for separating said rollers from each other along saidcircumferential path such that said rollers are prevented from skidding,said spacer means including a shaft fixed to said table and a hubrotatably mounted on said shaft with each of the fixed arms mounted onand extending outwardly from said hub, and said hub formed with aninternal bearing surface for engagement with external bearing meansmounted on said shaft, and said internal bearing surface and saidexternal bearing means configurated to afford axial and pivotal movementof said spacer means with respect to said shaft.
 2. Apparatus accordingto claim 1 in which said external bearing means includes a sleevebearing located in a position spaced apart from the end of said shaft,and a thrust bearing mounted on the end of said shaft.
 3. Apparatusaccording to claim 1 in which said contact means includes a replaceableblock having a frustoconical crosssection, and said replaceable block ismounted on the end of said fixed arm.